Structures Congress 2017: Bridges and Transportation Structures

Previous research and design codes have focused on developing equations, mostly empirical based on experimental studies, to determine the bond strength of steel bars with different types of concrete. However, limited studies have been conducted on FRP bars particularly embedded in self-consolidating concrete (SCC), but very few using aramid fiber reinforced polymers (AFRP) bars. This investigation aims to study the influence of two main parameters: (1) superplasticizer dosage and (2) water to cement ratio on the bond strength and bond slip model of the AFRP bars and SCC. Results show a significant effect of superplasticizer on the bond strength of AFRP bars embedded within SCC. Moreover, the effect of the w/c ratio is quantified and its correlation with bond strength is presented. The slippage of the AFRP bars embedded in the concrete was accurately measured to determine a precise bond-slip model that is compared to conventional concrete performance.

The Dolores River Bridge in Bedrock, Colorado carries SH-90 over the Dolores River. The bridge is in a remote location and crosses a channel that has the potential for deep scour during the extreme flooding event. The structure was designed with a combined focus on cost, constructability, and hydraulic performance during both the design and extreme events. The superstructure consists of concrete bulb tee girders and precast deck panels and the substructure consists of steel H-piles with precast concrete abutment caps. All bridge components except the barrier curb were designed using precast concrete elements because the site location is far from ready-mix concrete plants. The precast elements were designed and detailed to connect using high strength threaded rods and tolerances were established to allow for field adjustment and avoid lengthy delays during construction. The 100-year flood event has the potential to lower the channel grade by nearly 17 feet. To mitigate this, the abutment walls and wing walls were designed using driven sheet piles with rip rap protection. For the 500-year extreme event, the abutment was designed to remain stable and allow the roadway embankment to be replaced, providing a much faster and more economical repair than a complete structural replacement. This paper presents the unique design challenges of this structure and the solutions that were developed and implemented to meet the challenges while providing a cost effective product. This paper will provide an understanding of bridge abutment design that combines deep foundations for structural stability during the extreme scour event and sheet pile wing walls for stability during the intermediate scour event. The paper will also provide an understanding of the design and detailing considerations for a bridge structure using entirely precast components.

This paper promoted a novel isolation bearing called high-performance isolation rubber bearings (HIRBs). Its stiffening material is flexible high-strength steel mesh. With large horizontal deformability owing to stable rolling-over, HIRB was further studied on its seismic mitigation effectiveness and efficiency by conducting shaking table tests on a 1/20 scale half extra-dosed cable-stayed bridge model. Dynamic responses were compared with numerical simulation results of fixed bridge and unbonded laminated rubber bearing isolated bridge, including peak acceleration and relative displacement responses and residual displacement. Deck peak acceleration was reduced by 40%~80% compared with fixed bridge. Maximum residual displacement was only 4mm, nearly 1/10 of unbonded laminated rubber bearing isolated bridge. It indicates that HIRBs are excellent isolation bearings for not only satisfied seismic mitigation ability but also superior displacement sustainability and control.

Field evidence from recent earthquake indicates that strong aftershocks have the potential to cause severe damage or even collapse to structures. This paper aims to investigate the influence of aftershock on the seismic performance assessing results of bridge considering cumulative damage effect. For that purpose, a damage evaluating approach for continuous girder bridge is employed that includes two integral parts: deteriorating numerical modeling and a combined damage index that considers both large deformation and cyclic loading effects. To investigate the influence of aftershock, a continuous girder RC bridge was selected and nonlinear incremental dynamical analysis subjected to mainshocks and mainshock-aftershock sequences was conducted. The fragility curves were finally generated. Comparisons were also made to investigate the difference of the result due to whether the cumulative damage is considered or not. From the analysis results, it was found that, for continuous bridges, aftershocks can considerably increase the seismic demand as well as fragility. In addition, for moderate damage fragility, the influence of aftershock is greater when cumulative damage is considered.

The use of integral abutment bridges (IABs) is widespread throughout the U.S.; the Midwestern state of Illinois is no exception, with this bridge type commonly utilized in the state. The proximity of southern Illinois to the New Madrid Seismic Zone creates concerns about the earthquake-resistance of IABs in this region. Recent research concerning the seismic response of seat-type abutment bridges has determined that the failure of abutment bearings and backwalls are important fusing mechanisms under moderate to strong seismic loads. However, only limited research has been conducted on the seismic response of IABs (especially in Illinois), which do not have the abutment bearings that allow seat-type abutment bridges to behave in a quasi-isolated fashion. Through the use of site-specific ground motions developed for various locations in southern Illinois, along with a set of IAB models created in OpenSees, this paper presents preliminary data concerning the seismic structural behavior of an IAB designed per current IDOT procedures

Post-tensioning by means of high‐strength tendons can be used to effectively increase the ultimate capacity of steel-concrete composite beams. In this paper, a numerical model is presented to simulate the nonlinear flexural behavior of composite beams strengthened with externally post-tensioned tendons. The accuracy of the developed numerical model is validated using existing experimental tests. The influence of various strengthening parameters is investigated to show the effect of the tendon profile, the tendon length, the degree of shear connection, and the fatigue loads on the response of the strengthened beams. The results demonstrate that the trapezoidal profile shows better behavior for the strengthened beams than the other profiles at the same tendon eccentricity. Applying post-tensioning along the full length of the beam helps to reduce the creation of fatigue cracks, which always start at stress raisers, and consequently increases the fatigue strength of the composite beam. It is observed that 80% degree of shear connection or higher is recommended to obtain the desired performance of the external post-tensioning force. Also, external post-tensioning effectively improves the flexural behavior of the strengthened beam under fatigue loads.

Thousands of bridge structures rely on grouted post-tensioned (PT) tendons to economically improve their structural capacity. However, problems with grouting techniques and grout materials has resulted in bridges with grout voids, chloride contaminated grout and soft grout. These problems have promoted corrosion and failure of PT tendons, some within 6 to 17 years of service. As a result of these PT issues the Florida Department of Transportation (FDOT) has spent more than $55 million (USD) repairing 11 PT bridges. Vector Corrosion Technologies (VCT) has developed a cost-effective corrosion mitigation impregnation technique to minimize corrosion of PT tendons and extend the service life of PT bridges. This paper describes the development and implementation of the post-tension impregnation (PTI) system used on grouted PT tendons. The PTI system was demonstrated for FDOT on the I-95/I-295 Interchange in Jacksonville, FL and PT tendon samples from the Ringling Bridge, Sarasota, FL. The system uses an impregnation material to impregnate the cement grout and form a corrosion resistant film on the surface of the steel strands. Testing confirms the ability of the impregnation material to travel over 250 feet along the length of PT strands, to soak into the grout surrounding a strand and to reduce corrosion by over 90%. Laboratory testing and field demonstrations confirm the effectiveness of this new technology for mitigating PT corrosion.

There are great economic incentives motivating the reuse of existing bridge foundations when obsolete, deficient, or deteriorated superstructures are replaced or retrofitted. In many cases, these foundations still have significant functional values. Substantial time and cost savings can be realized when existing foundations are reused, and any capacity obtained from existing elements reduces the need to install costly new elements. While existing foundations have demonstrated load carrying capacity, many also have uncertain properties due to incomplete background information or lack of access for integrity and deterioration evaluation. In some cases, existing foundations may require strengthening, retrofit, or improvements for potentially higher or different loading conditions. This research proposes a simplified and practice-based approach to maximize the usefulness and available capacity of an existing foundation that can meet the target reliability prescribed by modern design codes. This is done by accounting for the static design equations, static load testing on individual piles, information on past loading history, and any load testing performed on the bridge.

A number of steel beam bridges exist in the United States that contain steel pin and hanger assemblies. Pin and hanger assemblies are fracture critical members whose failure would render a bridge unable to perform its expected functions or could possibly result in its collapse. As these bridges continue to age, many assemblies have deteriorated to a point where retrofit or replacement has to be considered and performed to maintain safety and performance. Departments of Transportation (DOTs) have used various approaches to address this issue. However, a detailed examination and compilation of methods that have been implemented and steps involved in their design and placement has yet to occur. Summarized herein is an ongoing synthesis project that attempts to document viable pin and hanger retrofit or replacement options in the United States. It is hoped that, at the completion of the project, findings would assist engineers with effective means to assess options and their benefits and consequences when pin and hanger assembly retrofit or replacement is being considered.

This paper describes design aspects of three pedestrian bridges that were recently completed: the main bridge of the San Ysidro East/West Pedestrian Bridge in San Diego, CA, the Blossom Hill Pedestrian Grade Separation Bridge in San Jose, CA, and the Montlake Bicycle/Pedestrian Bridge in Seattle, WA. The 806’-6”-long main bridge of the San Ysidro East/West Pedestrian Bridge over I-5 freeway consists of a cast-in-place prestressed concrete box girder superstructure supported by highly skewed pier walls with pile foundation. The 314’-6”-long Blossom Hill Pedestrian Bridge across the SR 82/UPPR Corridor is a two span continuous structural steel tube truss bridge with an overall structure depth of 12’-0”. The 427-foot-long Montlake Triangle Pedestrian (MTP) Bridge structure spans Montlake Boulevard near the University of Washington campus. The MTP Bridge is one of the first applications of a highly curved post-tensioning concrete structure in the United States. All of these pedestrian bridges were designed by AECOM. The specific structural challenges in design for these structures will be discussed herein.

When you hear “Mushroom Bridge”, you may very well think of Mario Kart. But it is also the nickname of a portion of the Crane Road Bridge, a nearly century-old crossing in north suburban New York City. Comprising two bridges, it carries the Bronx River Parkway through a forest preserve in the Village of Scarsdale and the Town of Greenburgh in Westchester County. The southern bridge is a multi-span concrete bridge (the Mushroom Bridge portion) that crosses the Bronx River, while the northern bridge is a single-span steel through-girder bridge that crosses the two-track Metro-North Railroad Harlem Line (accordingly called the MNR Bridge). In this project, the historic bridges are replicated to preserve the community while improving pedestrian use, access and enhancing the roadway geometry.

The construction of the main span of the new champlain bridge presents two main challenges. The first one corresponds to the construction schedule, as the bridge has to be opened within 2018. The second one is the requirement to minimize any impact on the seaway channel traffic during construction. The aim of this paper is to explain how those challenges have influenced and led to the elaboration of an innovative erection scheme designed to feed the gantry at the tip of the deck without interfering with the navigation channel. The system consists of a movable lifting beam, which lifts the segment up to the deck. The segment is then transferred to a trolley system which delivers it to the tip traveling underneath the deck. Finally, the segment is received by a dynamic lifting frame, which holds the segment at the tip of the deck until it is bolted.

Long-span bridges are flexible and therefore are sensitive to wind induced effects. For investigating the response of a bridge under wind loads using wind tunnel testing, aerodynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. The effect of Reynolds number can be amplified on multi–girder bridges. For investigating the effect of Reynolds number on the vortex shedding for modern bridges, a 2D section of a twin-deck bridge is evaluated analytically using computational fluid dynamics (CFD) and the results are compared with experimental results from large-scale tests performed in the Wall of Wind facility at Florida International University. CFD analysis was performed using vortex discrete method. Based on the results from this study, a similar trend is observed for the Reynolds sensitivity between the experimental and numerical results. Both methods show a reduction in the drag coefficient with the Reynolds increase up to 4×10⁶. However, with the additional increase of Reynolds, drag coefficient increases.

Distortion-induced fatigue is a serious problem faced by many aging steel bridges, and the problem is often exacerbated in skewed bridges. When distortion-induced fatigue cracks do occur in skewed systems, they can be especially difficult to repair. In situations where cross-frames are carried parallel to the skew, the connection to the cross-frame members is angled, presenting a geometric challenge during repair and non-symmetric loading of the detail. A retrofit called the angles-with-plate retrofit was previously developed at the University of Kansas for repairing distortion-induced fatigue damage in non-skewed steel bridges. The retrofit was subjected to a series of rigorous tests, and its good performance was the motivation to study the performance of the repair detail in skewed connections. This paper presents physical tests of the angles-with-plate retrofit conducted on girder subassemblies with 20 deg. and 40 deg.-skewed cross-frames. The tests were used to study the efficacy of the retrofit in mitigating fatigue crack propagation and localized deformations. It was found that crack propagation rates were drastically slowed while the retrofit was in place on the 20 deg.- and 40 deg.-skewed girder specimens, indicating good performance of the adapted angles-with-plate retrofit in this application.

A significant percentage of the steel bridge inventory is approaching or has surpassed its intended design life. Due to limited replacement funds, methods for increasing the service life, while maintaining safety, are of increasing importance. Most large steel bridges constructed prior to the mid-1960s are composed of riveted built-up members which, based largely on anecdotal evidence, have demonstrated resilience to failure through member-level redundancy. This internally redundant behavior of built-up steel girders provides a member with the ability to resist collapse in the event of a failure of an individual component. However, due to the lack of experimental data, built-up steel girders are currently required to be inspected as fracture-critical members when deemed non-redundant in a bridge system, and therefore do not take advantage of the redundant behavior of the members. A full-scale experimental research program was carried out to evaluate the fracture resilience of built-up steel girders. Parameters affecting the remaining load capacity of partially failed sections were also investigated. Specimens were then cycled in fatigue to determine their fatigue life in the partially damaged state. Results from this study were used to develop recommended assessment procedures for built-up members containing a failed component. Additionally, proposed specification language has been developed for inclusion in the AASHTO evaluation specifications. These provisions will permit the removal of the fracture critical classification for existing and new bridges in which built-up members meeting specific criteria are utilized. In cases where sufficient capacity exists and the fracture critical designation can be removed, guidance on setting a rational in-service inspection interval as well as inspection level of detail have been developed.

Impact factor formulas used for traditional rail bridges (AREMA) or highway bridges (AASHTO) cannot be assumed for high speed rail application. Trains crossing through a wide range of speeds are likely to have a case which drives a forced vibration that resonates with the dynamic behavior of the bridge. Because these bridges are excited for a short time, the transient response has shown to be significant, making simplified use of steady-state modal analysis inadequate. Several high speed rail bridges of various configurations in the California area were studied. Impact factors were computed based on the ratio of dynamic response to the corresponding static case. To compute the full dynamic transient response, a series of time-history analyses were performed on a finite element model. This study considered different train sets at speeds ranging from 90 to 250 mph. In addition to analysis of moving loads, vehicle-bridge interaction was considered by utilizing a series of moving mass-spring-dampers with multiple degrees of freedom and stepping those elements across the bridge. For the responses considered, it was shown that in most cases the critical impact factors were considerably larger than those calculated using AREMA or AASHTO equations. However, the inclusion of vehicle-structure interaction can help in reducing these large impact factors.

The Longfellow Bridge Rehabilitation Project is a design-build project, undertaking the rehabilitation of a century old multispan steel arch structure and its iconic “salt and pepper shaker” towers. Within the same project, sitting in the shadows of the Longfellow, sits a nondescript and inadequate pedestrian bridge, soon to be replaced with the Fanny Appleton Pedestrian Bridge, named after Longfellow’s wife. The Appleton, a 750 foot long structure, with 550 feet of elevated bridge including a 222 foot main span which mimics the arch spans of the Longfellow but with a very different and contemporary approach curving “ribbonlike” through existing trees. The main span, a spandrel arch supported deck made up of diverging 18 inch diameter pipe arches and HSS spandrel columns, was analyzed as a Vierendeel truss and the entire superstructure modeled in 3-D to capture stresses of steel erection through the temperature induced stresses of the jointless, curved superstructure. The architectural design also included steel Wye approach piers with an inset detail. This geometrically challenging form led the contractor, fabricator, and designer to choose a steel casting used within the steel pier assembly to create the unique detailing. On a daily basis, the route is a heavily traveled multi-use path for walkers, runners and bikers but on the 4th of July, it carries shoulder to shoulder crowds from the city to the Esplanade for the televised Boston Pops Concert and Fireworks. The project’s goal was to mitigate pedestrian induced vibrations without the use of tuned mass dampers while still meeting the architect’s aesthetic intent. The bridge’s function and aesthetics led beyond vibration criteria of the AASHTO LRFD Design Guide Specifications for Pedestrian Bridge to SETRA (Service d’Etudes Techniques des Routes et Autoroutes). A 3-D multi-mode vibration analysis was performed applying dynamic loads to target multimodal frequencies. Each element, including the foundations, was evaluated for its strength and stiffness in contributing to vibration performance. Piles were assessed using a bounded range of soil stiffness for stress and vibration performance. STV Inc.’s design balances strength, service, and user experience within the confines of aesthetic requirements, contract requirements, and constructability. The bridge is currently under construction.

High-speed rail transit continues to expand globally and is beginning to grow in the United States. The velocity of high-speed rail transit, relative to other rail transit, leads to an increased sensitivity to vibrations as it pertains to passenger comfort and safety. However, the range of travel speeds and repetitive uniform load patterns leave high-speed rail structures susceptible to resonance effects and large dynamic amplification of live loads. This necessitates dynamic analysis to investigate deformations, deck acceleration, and dynamic live load impact factors for all high-speed rail structures. Herein will be discussed an investigation as to whether the dynamic analysis of simple-span structures can be simplified to analyze only vehicle speeds corresponding to resonant action of the structure. Included in the investigation is a description of the dynamic analysis methods employed, investigation into resonance effects, conclusions reached for multiple case studies, and suggested best-practices for dynamic analysis of simple-span high-speed rail structures.

Railway bridges are subjected to various types of dynamic loading. Among these, earthquake, wind and vehicular loading deserve attention. Only vehicular loads are considered in this work. In many codes, such loads are considered as static loads which are multiplied by an impact factor to account for dynamic effects. Such procedure, although very likely conservative, does not consider the forces due to mass, damping and stiffness as in a typical dynamic analysis. Thus, it is the objective of this presentation to discuss a methodology that considers the interaction between railway vehicle and bridge in which both structures are modeled separately and have their specific dynamic characteristics. The bridge is modeled by finite elements and the vehicle is modeled as an assemblage of rigid bodies. The source of dynamic loading is track irregularities, which may have specific profiles associated with specific causing phenomena or may have a random profile as a result of the superposition of several causes. The analytical methodology is a complex result from the association of many modeling aspects that are put together to better represent the behavior of the bridge structure.

A computational framework for automated shape modification of long-span bridge decks is proposed. The proposed technique involves the use of computational fluid dynamics (CFD) for aerodynamic analysis, surrogate models for response function approximation and numerical optimization routines for iterative selection of optimal shapes. A brief review of aerodynamic shape modification measures for decks of long-span bridges is presented. The framework is applied for aerodynamic fairing design of a typical plate-girder stiffened deck with the objective of reducing the lateral wind load and improving aerodynamic stability under smooth flow. Numerically evaluated optimal fairing shapes are compared with that of Bronx Whitestone Bridge and Deer Isle Bridge. It is shown that sharper triangular fairings are effective to reduce wind induced drag, but shorter fairings with height around 60% to 70% of deck depth are effective to improve the aerodynamic stability of elongated H-shaped decks. Furthermore, asymmetric triangular fairings are found to be effective to improve the aerodynamic performance of asymmetric decks.

The current AASHTO Guide Specifications for LRFD Seismic Bridge Design and the Seismic Provisions contained in AASHTO LRFD Bridge Design Specifications are mainly based on prescriptive design methodologies that only marginally relate important design parameters to the seismic performance of bridges. With the current specifications, a designer does not have direct control over the seismic performance of bridges, other than to ensure that their capacity exceeds the demand. In recent years, there is an emerging need for bridge designers to be able to incorporate multiple levels of seismic performance into bridge design based on owner’s input and budgetary considerations. The new performance-based seismic design (PBSD) methodology enables engineers to make informed decisions about the seismic performance of bridges through incorporation of different seismic hazard levels and a multitude of operational expectations. Once incorporated, this design methodology allows designers and owners to better understand and quantify the seismic performance of bridges while considering its post-earthquake designated functions such as instant access by emergency responders or immediate availability for traffic. Although PBSD is relatively well developed for buildings, its application to bridges is still at a nascent stage. There is therefore a need for a clear and consistent approach to relate typical engineering demand parameters (EDPs) like displacements or strains, to potential damage (e.g., concrete spalling and cracks, steel yielding and fractures, instability or excessive elastic or permanent deformations) to the risks associated with such damage (e.g., loss of life, substantial repair costs, and downtime or indirect risks such as productivity slowdown and economic loss). This paper examines some existing knowledge gaps in implementing PBSD to highway bridges and proposes a framework to close some of these gaps. The proposed framework will provide more clarity toward a more meaningful assessment of bridge performance and evaluation of its potential use following an earthquake.

Ultra-high performance concrete (UHPC) connections used in modular bridge deck construction enhance the overall performance of bridge superstructures. Despite of numerous experimental studies on the UHPC connections, however, there is little numerical study on the performance and damage prediction of steel fiber reinforced cementitious composites under static and cyclic loading. Of particular interest in this study is the proposed mesh-free analysis method which can represent fiber-concrete bond and bond failure between the cementitious paste and steel reinforcement to ultimately allow a redesign of the UHPC connections by analysis and enhance their long-term performance. This study develops a mesh-free discrete modeling approach based on the bond-based peridynamics theory to study the response of modular bridge deck UHPC connections under static and cyclic loading. It is concluded that the proposed mesh-free analysis method adequately predicts the response of UPHC connections under static and cyclic loading and thus is promising to predict the performance of UHPC members.

There are over 215 million daily crossings on 61,064 U.S. structurally deficient bridges in need of repair. The U.S. Federal Highway Administration (FHWA) has rated almost 200,000 bridges, or one out of every three bridges, as structurally deficient or functionally obsolete. The annual direct cost of corrosion for highway bridges is estimated to be $13.6 billion (2014 U.S.$). The objective of this project is to provide a proper definition of structural resilience and associated metrics in order to acquire the capability of fully restore the functionality following an extreme event of any structure. For this purpose, the resilience metrics will be reviewed and simplified to develop the measurement science to assess the resilience of structures through the use of risk-based analysis and decision-making methods. The process of recovery will also be exhaustively examined, whether from deliberate attacks, accidents or natural occurring threats or incidents, as it is consider the main basis of resilience. Five case studies will be developed to illustrate the theoretical content of the project.

The size and complexity of the problem of maintaining the aging U.S. transportation infrastructure system, combined with the shortage of resources, necessitates an efficient strategy to prioritize the allocation of funds. Within the suite of tools available for decision-making for bridges, a fundamental characteristic is safe load carrying capacity. This capacity measure typically requires knowledge and data on the structural details of the constituent members to enable predictions of available resistance relative to loading demands. Bridges that receive low ratings and are deemed incapable of carrying the required loads are “posted” with maximum weight limit signage. This paper introduces a data-driven solution that enables the automated, rapid, and cost-effective evaluation of load postings for large infrastructure networks. The method proposed in this paper involves leveraging the large bridge population in the national bridge inventory and the associated bridge descriptors such as geometrical, operational, functional, and physical features, to extract and define patterns for predicting posting status. A cost-sensitive random forest classification algorithm was trained on over 280,000 bridges in selected categories in the national bridge inventory including steel, reinforced concrete, prestressed concrete, and timber bridges. Performance evaluation of the models demonstrated the validity of the models and comparisons with a number of other common classifiers was presented. The trained models were capable of detecting posted and unposted bridges with an average error of about 11% and 16% respectively. The trade-off between safety and economy in the models was also studied. Finally, as a product of the data-driven approach, an interactive software interface was developed which accepts user input data on bridges and predicts the posting status. This tool is expected to provide an intuitive method for rapid screening of bridge inventories and estimating deterioration progression, thereby resulting in substantial safety and financial benefits to owners.

Steel plate girders have been used as bridge structural components for over two hundred years. Given technology and material advancements, steel plate girders and their elements (webs and flanges), continue to become slenderer. As a result, elastic buckling is a concern when evaluating shear capacity. This issue has been addressed for straight girders by a number of researchers, most notably via the development of the theory of tension field action (TFA). To date, horizontal curvature effects have not been included in design of steel bridges, however others have investigated horizontal curvature effects on slender, shear panel behavior and capacity (1). This paper summarizes an ongoing study investigating how horizontal curvature influences the shear buckling capacity and ultimate shear resistance in steel plate girders with slender webs. Results show that horizontal curvature can affect the shear capacity and a proposed shear buckling coefficient produces accurate results.

Railroads have a long history of bridge measurement and monitoring — typically for purposes of structure protection or load capacity rating. In recent years, a number of vendors started offering structural health monitoring (SHM) systems, which take numerous measurements and market bridge life extension. This paper offers an overview of the fundamentals of railroad bridge monitoring and measurements, as well as examples and suggestions for appropriate use of each. Key issues discussed include: Targeted applications are most effective for any railroad bridge monitoring, measurement, and SHM efforts. Several bridge monitoring or protection systems are already in regular use by most railroads, although they might not fit the current marketing definition of SHM systems. One-time, short-term bridge measurements can be beneficial; particularly in conjunction with load capacity rating. Periodic monitoring can be beneficial and often is more appropriate than full-time SHM. Railroads generally need actionable information rather than the vast quantities of data potentially available from SHM systems. Any new systems should be highly reliable to keep false alerts, unplanned maintenance, and resulting service interruptions to a minimum. SHM systems can be beneficial in monitoring existing, older bridges. SHM systems need to be as maintenance-free as possible, or the cost of maintenance and the track time needed to perform it will offset potential benefits.

Many steel bridges in the United States designed before the mid-1980s are highly susceptible to distortion-induced fatigue cracking. This vulnerability is substantially increased if the out-of-plane driving force caused by differential girder displacement is increased for any reason. This research examines one such case where a multi-girder steel bridge, originally built in the 1960s, was retrofitted to improve seismic performance. As part of the retrofit, single angle K-type cross frames were replaced with stiffer double-angle cross-type frames. This seismic retrofit led to an increase in the driving force, and after only a few years following the retrofit, numerous fatigue cracks were identified in the web-gap region. Repairs were implemented to provide a positive connection between the connection plate and the girder flange aimed to reduce the level of distortion in the web-gap. This study presents the results of two field tests, before and after repair, and investigates the efficacy of the repair implemented for the bridge.

In the design of concrete bridges an important aspect is limiting crack widths, since large cracks can lead to e.g. corrosion and affect the bridge functionality. Restraint forces caused by thermal loads and shrinkage will likely constitute a large part of the total forces acting on the bridge in crack width design. In this paper, restraint stresses in portal frame bridges are calculated according to Eurocode with simple hand calculation models, 2D frame models and linear elastic 3D FE-models. The results are then compared and used in Eurocode crack width design methods. Large tensile restraint stresses were found in the transverse direction close to the frame corners, and the required reinforcement amount significantly exceeded the minimum reinforcement prescribed by codes. The results are however unrealistic since the thermal load distribution is simplified, and the crack width formula does not take the reduction of restraint stresses due to cracking into account. Future studies shall therefore determine a more realistic thermal load distribution and the effects of cracking, in order to create a more accurate linear elastic 3D FE design method.

Although extensive research efforts have focused on the design and response of structures under isolated earthquake loading or tsunami inundation, very few studies have considered their combined effect. Moreover, very little research has been conducted on heavy timber structures such as timber pile bridges. This study focuses on the performance of timber pile bridge substructure retrofitted with fiber reinforced polymer (FRP) composites subjected to earthquake-tsunami hazard events. Due to their simplified design, and susceptibility to deterioration, timber pile bridges may not have the capacity to resist extreme loads. FRP composites have become a popular material for structural retrofits due to their high strength, versatility, and because they do not corrode. Experimental studies have shown FRP composites can significantly improve the strength and stiffness of timber piles. In this study, the multi-hazard analyses are performed using the Open System for Earthquake Engineering Simulations (OpenSees) framework. Recently, OpenSees was extended to solve fluid-structure interaction (FSI) problems using the particle finite element method (PFEM). This new capability is used to simulate the tsunami loading. The goal of this study was to develop a multi-hazard interaction diagram to evaluate the impact of timber deterioration, and the level of FRP retrofit on the performance of the structure. The interaction diagram provides a useful means for engineers to estimate the performance of a structure and can be used to aid in repair decision-making.

The Long Island Railroad (LIRR) is typically either the busiest or second busiest commuter railroad in North America, bringing hundreds of thousands of Long Island and Queens residents into Manhattan and Brooklyn on a daily basis. When the Forest City Ratner Companies (FCRC) proposed to develop a new arena (Barclay’s Center) in Brooklyn so as to move the New Jersey Nets basketball team to Brooklyn, they evaluated several sites and settled on the developing the air rights over the 10 track depressed LIRR rail yard adjacent to their terminal station under Atlantic Ave in downtown Brooklyn. It was after all the first chance in more than a generation to bring a professional sports team back to this borough of approximately 2.6 million people since the Dodgers left in 1957.

A repair technique for severely damaged cast-in-place and precast concrete bridge columns has been developed that utilizes a carbon fiber-reinforced polymer shell and epoxy anchored headed steel bars to relocate the column plastic hinge. This shell encloses the headed steel bars and is filled with non-shrink concrete to a certain height to form a repair “donut”. The repair also employs a steel collar with steel studs that is attached to the column to increase the bond between the column and repair concrete. Three columns were repaired using the repair method described. The repair successfully relocated the plastic hinge at a section adjacent to the “donut” and was capable of restoring the load and displacement capacity. The steel collar combined with the “donut” were effective in making the repair system work in a composite manner. The method is rapid and could be classified as an accelerated bridge construction technique.

Bridges designed to resist earthquake ground-motions are expected to control the ambient vibrations acting through them. These vibrations are to be dissipated during major seismic excitations. This research is focused on the design of a self-centering friction damping brace (SFDB) for the dissipation of such seismic ground-motions. The dissipation is achieved through friction and the super elastic nickel-titanium shape memory alloy wires which are used to gain the self-centering action. The objective of this research is to experimentally evaluate the performance of a SFDB for future research involving the retrofit of the Vincent Thomas Bridge in San Pedro, CA, which experiences significant ambient motion. A small scale SFDB was designed, fabricated, and tested by loading the brace cyclically to failure. The results are compared to those of similarly-scaled linear viscous dampers. The force-deformation and energy dissipation characteristics of the SFDB are to be implemented in a model of the Vincent Thomas Bridge to determine its suitability for implementation as a retrofit strategy.

In recent years, considerable attention has been focused on the use of ultra-high performance concrete (UHPC) in highway construction for its superior properties such as significantly higher compressive strength and tensile strength than conventional concrete, minimal long-term creep or shrinkage, and exceptional durability, which helps to reduce joint cracking and enhance load transfer in the structures. A 3-D finite element model for understanding the influence of impact loading is somewhat lacking. The response of a beam under impact loading might depend largely on the extent of the local damage experienced due to impact loads. This paper investigates the global structural response of UHPC beams strengthened using CFRP (carbon fiber reinforced polymers) under impact loads. Due to the lack of experimental and numerical research on this topic, the study is conducted using the explicit finite element computer program ABAQUS. The numerical study is verified using the results of strengthened reinforced concrete beams under static loads. Four beams were considered in this study; two conventional and two UHPC beams. Two of the four cases were analyzed without CFRP strengthening and the other two were with CFRP. The impact load was considered equivalent to initial velocity of 100 in/sec. acting at the midspan of all beams. It is concluded that modeling UHPC is feasible in ABAQUS however the lack of the UHPC stress-strain relationship. As anticipated, UHPC showed less deflection, more energy absorption and less concrete damage compared to conventional concrete.

Unbonded post-tensioning strands have been employed in numerous research studies for precast concrete bridge piers to provide restoring force under seismic loading. When designing these systems, premature fracture of strands due to stress concentrations at anchorages and post-tensioning losses should be considered. Previous studies on unbonded strands between post-tensioning anchorages under cyclic loading are limited to 12.7-mm and 15.2-mm diameter strands and have been largely based on small-scale testing. Only a few of these studies reported post-tensioning losses. This research assessed the behavior of post-tensioning strands under cyclic loading to fill these gaps. The experimental program included 12.7-mm, 15.2-mm or 17.8-mm diameter, seven wire, 1860 MPa ultimate strength, low-relaxation strands between standard anchorage chucks. Stress-strain relationships and the anchorage wedge-seating of post-tensioning strands under cyclic loading were obtained. Post-tension losses were predicted based on the small-scale results and compared to the loss of a large-scale case study.

A three-column bridge bent of an actual bridge constructed in 1963 in Salt Lake City was evaluated for seismic load capacity and displacement ductility. The bridge was constructed before the 1971 San Fernando earthquake, and as such was missing the reinforcement details necessary to provide adequate load capacity and displacement ductility. Two seismic retrofit schemes, the first using buckling restrained braces (BRB) and the other using self centering braces (SCB), are examined in this paper. The BRB inelastic behavior is represented using the Menegotto-Pinto model to reproduce isotropic and kinematic strain hardening properties. Flag-shaped hysteresis with slip deformation and bearing is used to represent the SCB. Nonlinear time-history analyses were performed to assess and compare the seismic performance of the bridge bent in the transverse direction for the as-built and retrofitted three-column bridge bent. The bridge bent was evaluated under several performance limit states using far-field records from FEMA P695, which were scaled to the maximum considered earthquake level at the site. The results show that retrofit with either BRB or SCB components improves the seismic performance of the bridge bent under serviceability and ultimate limit states by decreasing drift demands, as well as maximum steel and concrete strains in the reinforced concrete columns. SCBs and BRBs reduce damage to concrete columns by dissipating energy. BRBs perform better than SCBs in reducing the peak drift of the bridge bent. However, retrofit with SCBs reduces the residual drift of the bridge bent for earthquake records with high peak ground accelerations to acceptable levels. SCBs are less effective regarding energy dissipation due to the flag shaped hysteresis but they keep residual drifts small, thus increasing resilience and keeping repair costs low.

Bridges are one of the most critical components of any transport infrastructure network, and their serviceability during earthquake is vital to ensure the safety of society. To be able to overcome bridge failure, code committees started to focus on different methods to design bridges under the effect of seismic forces. One of the challenges associated with Eurocode 8 and AASHTO-LRFD, which is not effectively addressed by code committees, is to withstand the failure of irregular bridges with unequal pier heights from seismic forces. EC8 currently uses “moment demand-to-moment capacity” ratios to ensure simultaneous failure of piers of bridges supported by piers of unequal heights, while AASHTO-LRFD relies on the relative effective stiffness of the piers. These regulations are not entirely valid, especially for bridges with piers of relative height of 0.5 or less, where in the case of earthquakes, they can experience a combination of shear and flexure failure modes. In this case, the shorter piers often result in a brittle shear failure, while the longer piers are most likely to fail due to flexure. This study aims to evaluate the adequacy of EC8 and AASHTO-LRFD design procedures for regular seismic behavior, by modeling various irregular bridges using shear-critical fiber-based beam-column elements. In this work the behavior of several irregular monolithic bridges is investigated. In addition, different methods of regularizing the bridge performance are examined in order to balance damage, with the ultimate aim of obtaining a simultaneous or near-simultaneous failure for all piers irrespective of the different heights and failure modes experienced.

This paper presents the results of an investigation into the impact of overloading of trucks on fatigue life of member details of an existing highway steel bridge. Different traffic scenarios were investigated by varying the percentage of overloading and number of overloaded heavy goods vehicles in the total truck traffic population using 2 axle, 3 axle and 4 axle trucks. The nominal stress approach was used for global fatigue damage assessment of member details of a bridge. The results show that heavy goods vehicles should not be overloaded beyond 20% of their maximum allowable GVW and the number of overloaded trucks within the traffic population should not exceed 10%. Overloading beyond this limits, increases the rate of fatigue damage to steel details by at least 20% and more. It was observed that a linear relationship exists between increase in GVW of heavy goods vehicles and fatigue damage to bridge details.

Experiences from previous earthquakes around the world have shown that a structure may face seismic sequences in a short period of time. Since there is not enough time for strengthening the structures during the time span between the earthquakes, the structures experience a level of degradation. Previous codes didn’t provide the requirements on seismic sequences effects on the bridges. Recently, some researchers studied the effect of multiple earthquakes on nonlinear behavior of RC columns. Many of the previous studies used artificial sequences to investigate the behavior RC bridge columns. The other important thing needing more attention is the effect of FRP confinement on the increase of structural performance. Therefore in this study nonlinear behavior of the RC piers of a bridge under as-recorded multiple earthquakes and for different FRP confinement levels are investigated. Results of this study indicate that considering a full confinement in piers may slightly improve the structural performance. Findings also show that the effect of the damage from the main shock is negligible for a long span bridge.

Creation of high-fidelity finite element models (FEMs) is an important prerequisite of finite element analysis which is widely used for assessing the health condition of structures and infrastructures. Currently, most FEMs are created by professional engineers based on as-designed condition. For aging structures and infrastructures, the as-is conditions might vary significantly from as-designed conditions due to accumulated damage. In order to capture as-is conditions, 3D laser scanners have become increasingly available because of their capability of capturing massive spatial data with high accuracy in a short period of time. However, currently, the creation of FEMs from laser scan data is still a manual process which is labor-intensive and might be error-prone. This research investigates an automatic approach of using spatial data from laser scanning along with computer vision techniques for creating high-fidelity FEMs automatically. Distinct point features from raw laser point cloud is established first. The extracted point features are then integrated with prior information available on the distributions and shapes of structural components for detecting and recognizing these components. Additional steps are proposed to extract geometric information for structural components with common shapes such as wide flange beams and cylindrical concrete piers. At the end, a methodology of converting point cloud data or extracted geometric information into all-hexahedral finite element meshes is presented.

Curved bridges are commonly constructed at interchange routes as connectors between two main roads in a highway network. Although past earthquakes, particularly the 1971 San Fernando earthquake, revealed the susceptibility of curved bridges to experience considerable damage during earthquakes, the seismic performance of this bridge class has not been investigated thoroughly. To address a part of this deficiency, the current study concentrates on the seismic performance analysis of curved concrete box-girder bridges with in-span hinges. In this bridge class, common potential damage patterns include damage to bearings and expansion joints, which are the most vulnerable components of the system. Hence, curved bridges including, in-span hinges, require particular investigations. As a case study, a highly curved bridge constructed before 1971 and located in California is selected for seismic analysis in this paper. The bridge seismic response is evaluated by performing nonlinear time history analysis in OpenSees on the representative bridge model with two configurations: (i) with an in-span hinge, and (ii) without in-span hinge (i.e. continuous deck). Moreover, the effect of superstructure curvature is evaluated by varying the radius of curvature from low to high (a bridge with a high radius approaches a straight bridge configuration). The analysis results indicate that curvature significantly affects the seismic response of the considered bridge, particularly for the model which includes an in-span hinge.

This study evaluates the effect of ground motion incidence angle on the responses of skewed bridges retrofitted with buckling restrained braces (BRBs) in the bents. A three-span skewed bridge with no retrofit is used as a baseline case. The assessment is carried out in OpenSees using a model that accounts for the BRBs between bent columns, abutment and shear keys, as wells as soil-structure interaction effects. The models are subjected to 21 far-field ground motions, and the maximum response under 11 incidence angles is obtained. The two components in each ground motion set are first rotated to their principal directions to minimize correlation among horizontal orthogonal directions. Thereafter, the ground motion components are scaled to the maximum considered earthquake (MCE) level. Nonlinear time history analyses indicate that seismic behavior of skewed bridges can be significantly different from that of straight bridges due to torsional effects caused by the combination of longitudinal and transverse seismic responses. The skew configuration decreases the difference in responses among different angles due to the combinational effects of longitudinal and transverse directions. After the retrofit implementation, the BRBs in column bents can mitigate the influence of incidence angle. Therefore, to predict the maximum bridge response is usually sufficient to apply the minor principal direction ground motion in the bridge longitudinal axis, and the major principal direction orthogonal to the longitudinal axis. The study shows that the use of BRBs as a seismic retrofit increases the seismic performance of the bridge components, reducing transverse drifts, abutment and shear key seismic demands; and reducing strains in bent columns.

In highly corrosive and saline conditions, such as bridges near salt water or those exposed to deicing salt, conventional structural steels experience high corrosion rates, and weathering steels fail to develop their protective coating. In contrast to conventional structural steels which are prone to corrosion when exposed to the environment, stainless steels are innately corrosion resistant. Therefore, stainless steel has been considered as a primary construction material in these saline environments to reduce the costs associated with repainting and maintenance of the structural steel. Recently, a new steel alloy, known as ASTM A1010, has been explored for use in plate girder bridges. ASTM A1010 is a 10.5-12% chromium steel with a higher level of corrosion resistance than conventional steel and weathering steel and a potentially lower cost than stainless steel. This study investigates the material properties of A1010 steel through tensile tests that were conducted on steel plate specimens. The monotonic tensile tests were performed following the ASTM specifications on base material specimens. In order to investigate the effect of plate thickness on tensile strength, specimens with three different thicknesses (½ in, 1 in, and 1¾ in) oriented parallel to the rolling direction were tested. For the plates with ½ in thickness, specimens orientated transverse to the rolling direction were also tested to reveal the effect of rolling direction on the tensile characteristics of A1010 steel. A video extensometer was used to obtain the strains during the tests and stress-strain curves were plotted. The overall mechanical behavior of the A1010 stainless steel was evaluated and compared with other steel types used in bridge construction.

Bonded post-tensioning tendons are used extensively in segmental bridge construction and have generally provided satisfactory service with respect to durability. However, multiple tendon failures in U.S. bridges with grouted tendons have led to the exploration of other forms of corrosion protection. One potential option is to use flexible fillers inside the tendon duct instead of cement grout that do not bond the prestressing strands to the concrete section. The use of these unbonded tendons not only affects the ultimate strength, fatigue, and serviceability behavior of structural systems, but also encourages efficient monitoring methods and facilitates tendon replacement during the structure’s service life. The current bridge design code, however, does not explicitly address flexible fillers, and little guidance is given regarding unbonded tendons in general. To evaluate the structural performance of unbonded tendons, full-scale experiments were conducted with both external and internal I-girder specimens having deviated tendon profile. These investigations provide important information on structural behavior of unbonded systems as well as tendon constructability, and can assist in the preparation of material and construction specifications. Multiple laboratory experiments were conducted with commercially available flexible fillers to examine the constructability of unbonded tendons. These experiments focused on tendon and duct detailing, filler material preparation, injection process and equipment, and venting procedures. An analytical investigation was also performed to compute the rate of cooling of flexible fillers during injection, which is a critical parameter to ensure that flow clogging does not occur. In addition, a promising tendon monitoring algorithm has been developed that uses the strain variations in the wedge plates caused by load relief due to corrosion-induced wire breaks. Extensive analytical and experimental investigations demonstrate the method’s feasibility in detecting, locating, and quantifying tendon damage.

The seismic fragility assessment of the bridge can be analyzed using fragility curves which is a method to estimate the probability of damage of the structure at a specific level of ground motion or an intensity measure (IM). The columns are the most vulnerable structural element in the bridges which have a significant contribution to the failure probability of the bridge system. This research presents the collapse fragility curves of non-seismically designed circular reinforced concrete (RC) bridge columns using different combination of parameters located in Vancouver, British Columbia, Canada. Probabilistic seismic demand models are produced using the results obtained from the incremental dynamic analyses. Considering collapse drift as a demand parameter, fragility curves are generated with different parameters of non-seismically designed circular RC bridge columns. It is observed that amount of reinforcement, shear span-depth ratio, and axial load are significantly affect the collapse fragility curve of the retrofitted bridge columns.

The Truckee River Bridge in Tahoe City, California, will provide bypass access around the city and facilitate trail access for bikers and pedestrians along the scenic Truckee River. The design incorporates many unique features to provide a cost effective and aesthetically appealing solution to carry highway traffic on the bridge and accommodate trail users below. The design features a simply supported main span using precast concrete deck bulb tee girders supported on cellular abutments. The cast in place concrete cellular abutments are innovatively designed to provide a top slab with minimal structural depth to support the roadway above and provide sufficient clearance for the trail below. The bottom slab of the cellular abutment was detailed to remain stable during the design scour and seismic events. The side of the cell adjacent to the channel contains large openings to provide unobstructed views of the river for trail users and provide natural light through the cell. Although torsionally eccentric, the cell was designed to remain elastic during the design seismic event and detailed to yield appropriately during an event that exceeds design levels. By understanding all the unique requirements of the project, the preliminary design was modified to provide the client with an ultimate solution that satisfies all required design codes while reducing the estimated design cost significantly. With a focus on speed of construction, the design was developed with modifications to streamline the structural geometry, simplify the superstructure type, and reduce foundation design requirements. This paper will discuss the iterative approach to transforming a complex preliminary design to an economical and constructable final design product. Also highlighted will be the design requirements and challenges as well as the innovative solutions that were successfully implemented during the final design of this project. These include the design of spread footing abutments for stability during the extreme scour event, the incorporation of cellular abutments and accelerated construction techniques to minimize project costs, and the seismic design of a torsionally eccentric cellular abutment.